The present invention pertains to computer numeric controlled (xe2x80x9cCNCxe2x80x9d) manufacturing machines and, more particularly, to portable CNC manufacturing machines.
One type of traditional CNC manufacturing machine has a bed with a base that is immovably mounted to the floor and a holding system that is immovably mounted to the base for releasably holding a workpiece. The traditional CNC manufacturing machine further includes a primary carriage that is movably carried by the bed and a secondary carriage that is movably carried by the primary carriage. The primary carriage is capable of being reciprocated relative to the bed along a primary path, and the secondary carriage is capable of being reciprocated relative to the primary carriage along a secondary path that is orthogonal to the primary path. The secondary carriage has a motor-driven spindle that includes an integral clamp for holding tools. The spindle can pivot relative to the secondary carriage, and the spindle can also reciprocate relative to the secondary carriage along a spindle path that can be orthogonal to the primary and secondary paths.
Such a traditional CNC manufacturing machine is ideal for situations in which a workpiece can be easily introduced to the holding system of the machine. However, it can be difficult or impossible to optimally introduce some types of workpieces to the holding system of the traditional CNC manufacturing machine, such as workpieces to which access is restricted and large workpieces. An example of a workpiece that can in some situations be difficult to introduce to the holding systems of some types of traditional CNC manufacturing machines is an aircraft wing or, more specifically, a wing that is connected to a fuselage.
Even though there may be a conventional CNC manufacturing machine that could be used to manufacture attachment holes through which bolts are received for attaching strut fittings to aircraft wings, it is conventional for CNC manufacturing machines not to be used in this process, which indicates that it is not cost-effective to use conventional CNC manufacturing machines for this process. In the current process, the attachment holes are xe2x80x9cmatched drilledxe2x80x9d on the wing in a vertical orientation, in wing majors. Spacing of the strut fittings relative to each other and relative to the wing is critical, so the fittings are accurately located on the wing using an alignment tool. The positions of the attachment holes in the strut fittings and overlying wing structure are established by using drill plates that are affixed to the alignment tool.
The drill plates are designed to retain power-feed drill motors (e.g., power-feed brand power-feed drill motors) that operate to spot face, drill and ream the strut fittings and overlying wing structure. A separate power-feed drill motor is setup for each tool. For example, if an attachment hole needs to be spot faced, drilled and reamed, then three separate power-feed drill motors are used. This results in a large inventory of power-feed drill motors and a considerable planning and support effort to have all of the equipment available to install the strut fittings. Power-feed drill motors are heavy, and it is physically difficult to manually position them on the alignment tools. Drilling an attachment hole in both titanium (strut fitting material) and aluminum (wing material) with a power-feed drill motor is a slow process. Titanium must be drilled at slow speeds (approximately 100-500 rpm), while aluminum can be drilled at higher speeds (approximately 1000-6000 rpm). With the current equipment, titanium paces the drilling operation and some holes take up to 18 minutes to drill. Additionally, hole patterns must often be shifted to adjust for xe2x80x9cedge margin.xe2x80x9d The drill plates make this difficult to accomplish. Additionally, access to the strut fittings for shimming and coldworking is difficult with the drill plates in position.
Accordingly, there is a need for improved CNC manufacturing machines and associated methods that can be efficiently used with workpieces to which access is restricted and large workpieces, and in particular that can be efficiently used for forming attachment holes for use in attaching strut fittings to wing structures.
The present invention solves the above and other problems by providing portable CNC manufacturing machines and associated methods that can, in accordance with one aspect of the present invention, be utilized to efficiently manufacture attachment holes for use in attaching strut fittings to wing structures, and that can also be utilized in the manufacture of other items.
In accordance with one aspect of the present invention, a method of manufacturing attachment holes initially includes assembling a workpiece. The workpiece is assembled by removably mounting an alignment tool to a wing structure so that the alignment tool holds a plurality of strut fittings to the wing structure. Preferably, the wing structure and strut fittings are conventional, and the alignment tool is at least partially conventional. The method further includes moving a subassembly of a CNC manufacturing machine to the workpiece and removably mounting the subassembly to the workpiece. Thereafter, the orientation of the workpiece with respect to the subassembly of the CNC manufacturing machine is quantified. A predetermined pattern of operations to be performed by the manufacturing machine to form the attachment holes is adjusted to compensate for the orientation of the workpiece relative to the subassembly. Thereafter, the CNC manufacturing machine forms the attachment holes.
In accordance with one aspect of the present invention, the alignment tool is conventional, except that it includes one or more fastener portions and one or more artifact structures. The fastener portions are utilized in the mounting of the subassembly of the CNC manufacturing machine to the workpiece. The artifact structures are utilized in the quantifying of the orientation of the workpiece with respect to the subassembly of the CNC manufacturing machine.
In accordance with one aspect of the present invention, multiple attachment holes are formed through a respective strut fitting and the overlying portion of the wing structure. A spindle of the CNC manufacturing machine is rotated at a first speed while drilling through the strut fitting and at a second speed, that is substantially greater than the first speed, while drilling through the overlying wing structure, with the drilling through the wing structure following immediately after the drilling through the strut fitting. Varying the speed of the drilling advantageously optimizes the drilling by compensating for the strut fittings being harder to drill into than the wing structure.
In accordance with one aspect of the present invention, the subassembly of the CNC manufacturing machine includes a frame, a positioning system for moving the frame to the workpiece, a mounting system for mounting the frame to the workpiece, at least one gantry carried by the frame for back and forth movement along the frame, and a carriage mounted to the gantry for back and forth movement along the gantry. The spindle is carried by, and moveable with respect to, the carriage. The spindle includes a removable integral tool holder for releasably holding the tools utilized by the CNC manufacturing machine to manufacture the attachment holes.
In accordance with one aspect of the present invention, the positioning system advantageously operates such that the subassembly of the CNC manufacturing machine can be conveniently moved into place with respect to a workpiece to be worked upon. Thereafter, the manufacturing machine can advantageously automatically orient itself with respect to the workpiece and form the attachment holes.
In accordance with one aspect of the present invention, the subassembly of the CNC manufacturing machine can advantageously be relatively light-weight because it is mounted to the workpiece in a manner that increases the rigidity of the manufacturing machine, so as to provide sufficient rigidity for accurately performing the desired manufacturing operations.